Abstract
The present study examined the effects of bicuculline on the mouse 5-hydroxytryptamine 3A receptor (5-HT 3A receptor and the human α2 subunit of the glycine receptor. Bicuculline antagonized both the 5-HT 3A receptor (IC 50=20.12±0.39 μM) and the α2 glycine receptor (IC 50=169.40±1.73 μM). A competitive form of antagonism by bicuculline was suggested by experiments in which the EC 50s for 5-HT and glycine were increased in the 5-HT 3A and α2 glycine receptors, respectively, as bicuculline concentrations were increased. A competitive nature of antagonism by bicuculline at the 5-HT 3A receptor was also suggested by displacement of the competitive antagonist, [ 3H]GR65630 in SF21 insect cells expressing the 5-HT 3A receptor ( K i =19.01±0.71 μ M). Our data and that of others reveal that bicuculline, a purported selective antagonist of the GABA A receptor, antagonizes at least one receptor subclass in every member of the superfamily of ligand-gated ion channels.
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